Hypochlorous acid (HOCl) is a weak acid that is known to rapidly inactivate bacteria, algae, fungus, and other organics, making it an effective agent across a broad range of microorganisms. Additionally, since hypochlorous acid is a weak acid and since people naturally produce certain compounds that allow them to tolerate hypochlorous acid (e.g., the amino acid taurin), it is generally not harmful to people. Due to the combination of its biocide properties and its safety profile, hypochlorous acid has been found to have many beneficial uses across many different industries, such as the medical, foodservice, food retail, agricultural, wound care, laboratory, hospitality, dental, or floral industries.
Hypochlorous acid is formed when chlorine dissolves in water. One manufacturing method involves the electrochemical activation of a saturated salt solution (e.g., brine) to form HOCl. Another production method involves the disproportionation of chlorine gas in alkaline solutions.
A problem with hypochlorous acid produced by these methods is that it is highly unstable, and over a short period of time (e.g., a few hours to a couple of weeks) the hypochlorous acid will degrade. The distribution of chloric compounds in aqueous solution is known to be a function of pH. As the pH of a solution containing hypochlorous acid becomes more acidic (e.g., pH below 3), chlorine gas is formed. As the pH of a solution containing hypochlorous acid becomes more basic (e.g., pH above 8) hypochlorite anions (OCl−; i.e., bleach) are formed, which are also toxic to people. Thus, while being an effective biocide, the use of hypochlorous acid has been limited by the need for onsite generation and the challenge of maintaining storage stability.